Grabbing clutch - grrr!

[penman]

Hi there,

When I first put my 500 back on the road, I gave the clutch assembly a good clean and replaced the oil seals. It was fine and continued to be fine for several years. Last year though, when I was preparing it for the Piston Rally, the clutch started grabbing. I had no time to do anything about it, so I set off, hoping it would get better. It didn't, it got much worse. By the end of the rally it was so bad, it was impossible to take off smoothly from rest. As soon as the clutch started to bite at all, it would grab violently and stall the engine. From rest I had to push the bike forwards until rolling and then release the clutch lever as gently as I could. After 2 or 3 kangaroo jerks I was away.

So this summer I have dismantled the clutch. There was some oil on the plates, not a lot but some. So I have cleaned it up, fitted new seals and new friction and metal plates, the old ones being a bit well worn by now. Knowing that the Morini clutch has a possibility of a kind of "self servo" effect, due to the helical primary gears tending to push the clutch further into engagement as they come under load, I also paid careful attention to the shimming. Well after all that, it's still a pretty bad clutch to use. It still tends to grab - not quite so badly, but badly enough to make it difficult to take off without stalling it. I will of course have another go at it, but I don't really know what to look for now. Any ideas or suggestions?

Many thanks,

Joe.

[BumbleBee]

Funny thing is as long as the basics (the bearing and also the end float and the hub/basket grooves, the plates and the clutch cable) are all ok people seem to say (on the 350 at least) it's all down to things like the condition of the chain and sprockets, the balance of the carburetors, and whether the engine is running cleanly as it takes up the load.

[norbert]

Do the enter hub have deep marks from the metal plates? If so you can pas a file to make it a bit better. And the second important thing is that one metal plates is still curved/domed! If I remember it well this plate is a bit thinner than the other ones. It used to become a bit blue from heat. If this plate becomes flat you will have these problem. I had the same issue with two 501 motors.

This one is realy a good one

k-DSCI0009.JPG (58.66 KiB) Viewed 3876 times

[3potjohn]

My 350 clutch which I put a new clutch pack in about 16 years ago has worked well. On my other Morini, a Coguaro the clutch was nowhere as pleasant in action with judder and an on/off action.The concave plate was flat. My original old pack from the 350 and subsequently a new one made a great improvement as did cleaning it all and taking any burrs off.
I shimmed the clutch on the 350 but I have not done this on the other bike.

[penman]

Thanks for the replies!

The bike is back up on the operating table and I'll dismantle the clutch again today. The clutch outer basket is in great condition with no significant grooves or marks in the splines. I will have another look at it though. I have also replaced all the friction and metal plates, so they "should" all be good, including that dished plate. Again though, I'll have another look and compare it with Norbert's photo - thanks for that! I will also check for float now that everything has had a chance to settle down after re-assembly.

I must say, the clutch was previously smooth and easy to use, up until last year. I never paid much attention to shimming because it seemed to work fine even with significant float. Anyway, I'll get cracking on it now and post an update on it later.

Regards,

Joe.

[72degrees]

When I was hill climbing the Forgotten Error I used to swap the clutch stack in from the road engine as I could never get the one with all new plates to have a nice take up. To get the best launch off the line you don't want a binary clutch. In the end I reckon it was a case of the plates on the 'nice' stack being mildly moist with a smidgen of oil mist from the 375 engine. The Weevee spring assisters (washers under the spring cups) make a slightly slippery stack not slip, it seems, but retain a progressive action.

[penman]

Good morning, and once again many thanks for your replies.

I did get it reassembled yesterday and I found two possible issues. First I now had a bit of float in the clutch basket, not a lot, about 0.2mm I would guess. Second, I am much obliged to Norbert for his photo, quite a nice way to both visualise and measure the amount of "dish" to the non-flat plate. As best I can judge, his plate was tilting up about 9mm. My new plate was only dished by about 4mm in the same test. I had a rummage through my Morini-related junk pile (I'm not very good at throwing stuff away!) and I found another dished plate measuring 8mm. So, I re-shimmed the inner clutch hub and fitted the 8mm plate. I had a ride this morning and it is a lot better - not "fantastic" but certainly acceptable. I stopped and started dozens of times and it was improving all the time, so I guess the new friction plates were bedding in and improving things.

Hopefully that's the end of this saga, I just have a few routine servicing issues to attend to and the bike will be ready for the Piston Rally - it's 5th time if my memory serves.

I might start a thread on experiences with the Sachse ignition system, I'll be interested to hear if anyone else has made this investment.

Regards,

Joe.

[norbert]

Hey Joe,

that´s fine you´ve found a more dished plate If it has become flat it´s realy a pain to start from being parked! It seem´s that this problem appears more often with 500 than 350, although the clutch is exactly the same (with the only diference of the bore in the center hub).

When will take place the piston rallye this autumn? Is it the event at Santander or Colombres? I´ve been there in Asturias and Cantabrica with my Morinis several times but never when the rallies took place

[penman]

Hi Norbert,
The Piston Rally starts on Sunday 17th September. I will take the ferry to Santander on 15th. I can give you full details if you want. It's a great event, I think I have been 11 times now!

Regards,
Joe.

[3potjohn]

I went three times back in 2007-2009 when at Columbres, though on a R60/7. Good times. Ought to go again, it is only a hop and a skip down to Plymouth too.

[BumbleBee]

There is a lot of experience of the Sachse ignition system out there in the club, probably mainly on the 350, some of it spread across posts in the forum. I know it has advantages such as adjustable curves and potentially better running. The standard system also has advantages, the Sachse system won't let you start the bike with a flat battery which my be important if you leave the bike unridden for periods of time. Also the standard system has three small types of component most of them are still "available" by which I mean either the original type or a newer/similar alternative, or a repaired one from someone who knows how. Certainly the standard system doesn't get the absolute best performance out of the engine but perhaps we are not all racing them these days.